Field of the Invention
The present invention relates to an outboard motor, and more particularly, to an outboard motor preferably employed in a ship model having an engine provided with a catalytic converter.
Description of the Related Art
An outboard motor mounted on a small boat and the like is configured such that an upper unit and a guide exhaust are connected to an upper portion of a lower unit provided with a propeller, an engine is supported and fixed on the guide exhaust, the engine is covered by an engine cover, and the propeller is rotated and driven by the engine. An exhaust gas from the engine is discharged to the seawater through an exhaust passage vertically provided on the side surface of the engine across upper and lower units. In such an engine of the outboard motor, a catalytic converter may be provided in the exhaust passage in order to purify the exhaust gas and comply with an exhaust gas control requirement.
For example, in Patent Document 1, there is discussed a outboard motor structure in which an exhaust gas cleaning catalyst is arranged in one of the side portions of the cylinder block, and the exhaust passage in the downstream side from the exhaust gas cleaning catalyst passes over the cylinder block of the engine and is guided to the opposite side portion in order to prevent flooding to the exhaust gas cleaning catalyst.
Patent Document 1: Japanese Laid-open Patent Publication No. 2009-197743
Meanwhile, in general, an external air inlet duct of the outboard motor is provided in an upper portion of a cowling. Waves or water splash generated by a ship hull may intrude into the external air inlet duct disadvantageously. A water separator capable of preventing intrusion of waves or water splash into the inside of the cowling is disposed in the upper portion of the cowling which is provided with the external air inlet duct. In addition, as discussed in Japanese Laid-open Patent Publication No. 2009-197743, a flywheel magneto 144, a timing belt 55 for driving a valve gear, or a flywheel magneto cover 200 for covering them are arranged in the upper portion of the engine in the outboard motor of the prior art.
It is necessary to arrange theses members or parts to detour the exhaust passage. In addition, since the exhaust passage 70 passes through the side of the cylinder block where the intake pipe (56) is arranged, it is necessary to provide a heat insulator for preventing overheating of the intake pipe 56. For this reason, in order to arrange the exhaust passage compactly in a relationship with neighboring members or effectively prevent flooding to the exhaust gas cleaning catalyst, the structure of the outboard motor becomes complicated and large-sized inevitably.